Testo 770-1 TRMS Clamp Meter – 400 A AC/DC, 600 V, Inrush Current, Retractable Clamp Jaw, CAT IV (0590 7701)

Testo 770-1 (product code 0590 7701) is a TRMS (true RMS) clamp meter designed for non-contact current measurement on tightly packed power cables and conductors. It measures 0.1 … 400 A AC/DC current and 1 mV … 600 V AC/DC voltage; its inrush current measurement lets you see the starting current of compressor and fan motors. Thanks to its gripping mechanism, every cable is gripped easily and safely.

Easy Current Measurement in Tightly Packed Switch Cabinets

The movable clamp jaw of the Testo 770-1 is fully retractable; this way, tightly packed cables in switch cabinets can be picked out one by one, as if using a hook. The instrument automatically detects and selects AC/DC as well as electrical parameters such as resistance, continuity, diode and capacitance; the large two-line display shows measurements clearly.

It is used for everyday electrical measurements in air conditioning, refrigeration and heating service, such as measuring current consumption, checking the voltage supply on live cables, continuity testing on switching components, and measuring the resistance of sensors and motor windings.

Technical Specifications (Official Testo Data)

• Brand / Model: Testo 770-1 TRMS clamp meter · product code 0590 7701
• Measurement Type: True RMS · basic accuracy 0.8%
• Current: 0.1 … 400 A AC/DC · DC current accuracy ±(2.0% of reading + 5 digits)
• Voltage: 1 mV … 600 V AC/DC · DC accuracy ±(0.8% + 3 digits) · AC accuracy ±(1.0% + 3 digits)
• Resistance: 0.1 Ω … 40 MΩ
• Capacitance: 0.01 nF … 100 µF
• Other Functions: inrush current measurement · continuity test · diode test · automatic AC/DC detection
• Display: two-line · 4000 counts
• Measurement Category: CAT IV 600 V
• Protection Class: IP40
• Power Supply: 3 × 1.5 V batteries
• Operating / Storage Temperature: −10 … +50 °C / −15 … +60 °C
• Dimensions / Weight: 243 × 96 × 43 mm · 378 g
• Approval / Standard: CSA/ETL, CE · EN 61326-1, EN 61140

Scope of Delivery

• Testo 770-1 TRMS clamp meter
• 1 set of test leads (0590 0010)
• Batteries
• Test protocol and instruction manual

Technician Tips

• Clamp a single conductor: when measuring current with a clamp meter, enclose only the phase or the neutral conductor in the jaw; clamping both conductors together shows a value close to zero because their fields cancel each other out.
• See the compressor start with the inrush current function: on a compressor that stalls at start-up or trips the overload protector, measure the starting current with the inrush current function and compare it with the LRA value on the label.
• TRMS matters in inverter circuits: in air conditioners with inverter boards, the current waveform is distorted; average-responding instruments are misleading, while TRMS measurement gives the true value.
• Disconnect power for resistance and continuity: carry out motor winding, sensor and contact measurements after the circuit has been de-energized and the capacitors have been discharged.
• Observe the category: the instrument is rated CAT IV 600 V; do not measure voltages above this value or use unsuitable test leads.

Technical document: Testo 770 clamp meter product brochure (PDF, Turkish)